Biomolecule-Assisted Hydrothermal Synthesis and Self-Assembly of Bi₂Te₃ Nanostring-Cluster Hierarchical Structure

Abstract

A simple biomolecule-assisted hydrothermal approach has been developed for the fabrication of Bi(2)Te(3) thermoelectric nanomaterials. The product has a nanostring-cluster hierarchical structure which is composed of ordered and aligned platelet-like crystals. The platelets are approximately 100 nm in diameter and only approximately 10 nm thick even though a high reaction temperature of 220 degrees C and a long reaction time of 24 h were applied to prepare the sample. The growth of the Bi(2)Te(3) hierarchical structure appears to be a self-assembly process. Initially, Te nanorods are formed using alginic acid as both reductant and template. Subsequently, Bi(2)Te(3) grows in a certain direction on the surface of the Te rods, resulting in the nanostring structure. The nanostrings further recombine side-by-side with each other to achieve the ordered nanostring clusters. The particle size and morphology can be controlled by adjusting the concentration of NaOH, which plays a crucial role on the formation mechanism of Bi(2)Te(3). An even smaller polycrystalline Bi(2)Te(3) superstructure composed of polycrystalline nanorods with some nanoplatelets attached to the nanorods is achieved at lower NaOH concentration. The room temperature thermoelectric properties have been evaluated with an average Seebeck coefficient of -172 microV K(-1), an electrical resistivity of 1.97 x 10(-3) Omegam, and a thermal conductivity of 0.29 W m(-1) K(-1).

Biomolecule-assisted hydrothermal synthesis of Bi2Te3 nanostructures

“…A detailed study of the hierarchical structure of Bi 2 Te 3 has been described elsewhere. 8 Only small nanoparticle can be obtained for sample S03. Bi 2 Te 3 nanoparticles as well as larger Te nanorods are found in sample S04.…”

“…In our previous studies, we have successfully synthesized Bi 2 Te 3 nanostructured materials by a biomolecule-assisted hydrothermal method, which is "green" and facile. 8,9 At the same time, biomolecules used as the mild reducing agents have strong size and shape directing functionality in the reaction process, which could be exploited to organize nanostructured materials with special morphologies. In this paper, we have carried out experiments to systemically study the effect of concentration of pH additives on the morphology and size of Bi 2 Te 3 nanostructures.…”

Green synthesis and formation mechanism of nanostructured Bi2Te3 using ascorbic acid in aqueous solution

“…2(e). Syntheses of disk-like Bi 2 Te 3 NPs with diameters ranging from approximately 10 nm-2.0 lm by various synthesis methods were widely reported [14,18,[21][22][23][24][25][26][27][28]. A rhombohedral Bi 2 Te 3 crystal has a layered anisotropic lattice structure with the Te and Bi atom layers arranged in the order of -Te (1) -Bi-Te (2) -Bi-Te (1) -along the c-axis direction [10].…”

Superassembling of Bi2Te3hierarchical nanostructures for enhanced thermoelectric performance

“…In practice, nanostructuring is broadly regarded as interfacial engineering for thermoelectric nanomaterials, since the abundantly formed interfaces involving various dimensions, topographies, structures and scales actually play dominative and multiple roles in strongly modulating charge carrier and phonon transport in matters [4][5][6] . In contrast to the preciselycontrolled interfacial engineering, most nanocrystals assembled bulk or films [8][9][10][11][12][13][14][15][16][17][18][19] , which also contain a relatively high interface density, typically show a restrictedly decreased thermal conductivity but also a seriously low electrical conductivity that appears to originate from the less regular interface arrangement and period, and more specifically, the high electric resistance of the incoherent or low-crystalline interfaces. 19 As superlattices, in which the well-designed interfaces successfully gain an outstanding ZT of ~1.5, evidently proving the role of interfaces in raising the electron filtering effects and subsequently having such a strong anisotropic Seebeck effect 7 .…”